The present invention relates to pneumatic guns of the semiautomatic or automatic type. The invention is particularly useful for firing marking pellets, also known as paintballs, but may also be employed for firing other projectiles such as darts, metallic pellets, or B-Bs.
The invention offers advantages of efficiency in the utilization of the propellent used by the gun, and of maintainability. Inefficient use of the propellent available to power a pneumatic gun is detrimental, reducing the number of shots which can be fired from a given supply. In addition, in the typical application where the propellent is initially in the liquid state and is converted to gas to power the gun, inefficiency also reduces the number of effective shots which can be fired over a short interval of time. The latter reduction occurs because each release of propellent to fire the gun requires heat to convert propellant fluid, typically liquid carbon dioxide, from liquid to gas. This heat loss causes a slight reduction in temperature of the remaining propellant fluid and a corresponding reduction in gas pressure available to continue operation of the gun. With rapid multiple shots this reduction in gas pressure can be sufficiently large, particularly in an inefficient gun, to significantly reduce projectile velocity, or even to prevent the gun from recocking until the propellent fluid has rewarmed.
It is previously known in the art to have semiautomatic or automatic pneumatic guns. Representative of this art are Tippmann, U.S. Pat. No. 4,819,609 (1989) and Merz, U.S. Pat. No. 3,103,212 (1963). Such pneumatic guns generally incorporate a gun frame, a grip, a barrel, a magazine of projectiles with a feed assembly for introducing a single projectile into position for firing, a source of compressed gas, a striker, a striker power spring, an operator actuable trigger mechanism with a sear for restraining the striker in a cocked position, and at least one valve, openable upon impact by the striker, for regulating release of compressed gas at the full pressure of the compressed gas source. During the firing phase of gun operation, the striker moves in response to urging by the striker power spring from the cocked position to a position of impact on the regulating valve, briefly opening the valving.
Also required to initially prepare the gun for firing is a method for manually moving the striker to the cocked position. A bolt for sealing the feed assembly against loss of the compressed gas released to the projectile then being expelled from the gun may also be present in the gun. In general, pneumatic guns are tuned to provide as high a velocity as can be achieved consistently, or as high a velocity as is permitted in the sporting event in which the gun is to be used.
Double-action trigger mechanisms provide one type of semiautomatic gun, generally with the first portion of trigger movement acting to cock the striker and the remaining portion acting to release the striker from its cocked position. In true semiautomatic and automatic guns, compressed gas released during firing provides the motive force which returns the striker to the cocked position. An automatic gun differs from a semiautomatic gun in not requiring an actuation of the trigger for each successive shot.
In general, the striker of a true semiautomatic or automatic gun functions in two modes, one during the firing phase of operation, and another during recocking. During the firing phase the striker, usually in a cylindrical striker chamber, acts as a hammer moving in response to the urging of a striker power spring from the cocked position to impact on, and briefly open, the regulating valving. During recocking, the striker acts as a piston moving to the cocked position and compressing a striker power spring in response to the force exerted by a charge of compressed gas provided to the striker chamber during firing.
The requirements imposed on these two modes of functioning are different. During the firing phase, the striker chamber should be vented to a region of nominally ambient pressure exterior to the striker chamber, so that striker movement toward the regulating valving is not impeded by gas trapped in the striker chamber ahead of the striker. During recocking the striker chamber should be sealed so that efficient use is made of the energy available from the compressed gas charge.
Merz and others use a single regulating valve, which during firing releases compressed gas into a main channel. One portion of the gas released serves to propel a projectile, and a second portion flows through an unvalved secondary channel to a striker chamber, where it acts to recock a striker. The disadvantage of the secondary channel being unvalved is that some gas in the striker chamber escapes by flowing back out through the secondary channel before contributing fully to recocking, but too late to contribute effectively to propulsion of the projectile, thereby reducing efficiency in utilizing propellent fluid.
Tippmann uses two valves contained in a slidable valve housing, both of which regulate the release of compressed gas at the full pressure of the propellent source. During firing, a striker impacts a first valve, releasing a charge of compressed gas into a striker chamber. In addition to serving to recock the striker, this charge of gas cooperates with the impacting striker to open a second valve which releases gas for expelling the projectile. As a first disadvantage, this doubles the number of full-pressure valves which must be maintained. As a second disadvantage, the initial release of gas for recocking, followed by the release of gas for projectile propulsion, encourages a relatively long total period of gas release. As is known in the art, a longer period of gas release results in less efficient use of the gas to accelerate the projectile being expelled from the gun, and hence results in greater consumption of gas to achieve a specific projectile velocity.
Given the ambient temperature range over which pneumatic guns are expected to operate, and the cooling of the propellent which results from multiple shots fired in rapid succession, the pressure in a propellent fluid reservoir which is not yet exhausted can vary by a ratio of more than 3 to 1. The charge of recocking gas, provided to the striker chamber during firing of a semiautomatic or automatic pneumatic gun, should provide sufficient force to reliably recock the gun at the lower end of this pressure range, but not so much force that gun components are damaged at the higher end.
Generally, variations in source gas pressure are partially compensated for in pneumatic guns according to the art. In these guns, the pressure of the source gas acts on the regulating valve mechanism when it is open and contributes to urging it to close. As a result, when source gas pressure is low the valve mechanism tends to open farther and be open longer during firing, providing more time for gas to enter the striker chamber, thereby compensating partially for the lower pressure. However, the compensation is only partial, as is evidenced by such guns demonstrating significantly greater excess recocking force when the weather is hot than when it is cold. Pressure regulators offer one means of compensating for variations in source gas pressure, but have the disadvantage of increasing gun complexity and hence gun maintenance. A need remains for improvements which will provide reliable recocking over a wider range of source gas pressures without significantly increasing gun complexity.
It is therefore an object of this invention to provide a semiautomatic or automatic pneumatic gun of improved efficiency in which striker motion toward a position of impact on the regulating valve mechanism is not significantly impeded by gas in the striker chamber, and in which compressed gas provided for recocking is not permitted to escape without contributing fully to the recocking process.
Another object is that the gun provide improved efficiency by virtue of permitting a short interval over which compressed gas is released during firing.
Another object is that the gun recock over a wider range of source gas pressures without a significant increase in gun complexity.
Another object is that the gun minimize gun maintenance by use of only a single full-pressure valve.
Further objects and advantages will become apparent from a consideration of the ensuing description and drawings.